Put in a new radiator, got problems. Advice?

[jtb1689]

So I went in recently to replace the gasket on the timing cover. While I was at it put in a brand new water pump and gasket, also did the intake manifold gaskets and valve cover gaskets all that good stuff along with a new radiator (oem equivalent). However I now have a problem. When driving, after accelerating (putting the rpm's up) and after I let the rpm's come back down, my temprature spikes. Either all they way up to the white line just before crossing into the red, or somewhere between the L in NORMAL and that white line. Then, after a few seconds, the temp goes back down to normal right where it should be on the R.

At first I thought maybe it was the thermostat, should have done it when I took everything else off anyway. So I did, still have the same issue. Maybe the water pump, but that is highly unlikely since It's brand new and coolant does flow. I checked the upper radiator hose when the temp spiked, it was completely pressureless, however it was nice and firm like it should be once the temp was normal. I'm pretty sure I've just got some airpockets from when I bled the whole system out replacing everything. So, on to the big question:

Is there a technique to burping the cooling system on these 1st gens? Or, any other ideas on what to do or what it could be? Any and all suggestions welcome. Thanks in advance, all you guys on here are awesome.

Edit: PS, No white smoke out exhaust and the only loss of coolant I've had is when revving the engine up with the radiator cap off, watching the coolant go down, then letting it rev down and have the coolant come spraying out. Everytime thinking maybe I got the air bubble only to find out it all happened again next time around.

 

[huntman58]

Just a thought here but some thing I have personal done or had happen to me to I will ask.
1 did you change out the thermostat?

2 did you maybe put it in backwards

3 did you check it out in hot water first to make sure it was good even if new before you installed it?

4 did you also change out all the coolant hoses including any by pass and heater ones besides the upper and lower main ones?

5 and my biggest goof did you happen to leave a rag in the motor and forget to pull it out when working on it?


I only ask because at one time or another I have had all of the above happen to me and had what your dealing with then also take place so just a thought. By the way every time I have changed a radiator out and not the hoses they have blown one by one with in a short time so now I replace them all to stop that part but I have had a new one collapse on me may want to check that also

 

[jtb1689]

All great ideas. Did replace thermo, and its in properly (with a new gasket/oring), didn't check in hot water first though. I didn't replace any of the hoses but I did check all of them for cracks with the good ol' fill it with water and bend it technique. And there's no rag in there, I've had that hood open at least twice a day looking in there trying to find something obviously wrong since monday, I'm sure I would have seen one, but I will check again to be sure . Maybe I will run out and buy up some new radiator and heater hose if I can find some locally tomorrow and replace all those to, if nothing else, prevent them from blowing soon.

Keep the ideas coming, they are all very appreciated

 

[surf]

Did you replace the timing cover gasket with the engine in the truck? If so, any comments or suggestions on how you did it would be greatly appreciated. Thanks.

 

[Albino 94LTD]

When I replace my radiator, the gauge would spike up and down but not that far. Its normal position was/is near the N.

After several weeks it still moved but not as much and even less now.

 

[Diff Whack Daddy]

I am not going to say it's common, but I too have had spiking temperatures after cooling system work. When it happened to me, the dealership replaced the water pump (under warranty a long time ago) and two blocks after leaving, the temp was on the high side of the L before it shot back down.

After a while though, it would stabilize and maintain a more constant temp. I would keep an eye on it, but the fact that thermostat is opening is evident by the temp quickly dropping and also proves you have adequate flow. Keep checking the fluid levels both in the radiator and the overflow tank (when cool) and as all the air eventually burps out, I think that it will start acting normal again.

 

[jtb1689]

So it is just a wait and see kind of thing. I guess on one hand that's good because I don't have to really do anything, just a little scary when it spikes like that. Not looking to blow a head gasket.

Don't know if it makes a difference but did your guys' do it consistently? I spike it seems like every 2 or 3 minutes. I think I forgot to mention also, I can stop the spike by revving the engine up, either while in drive or in neutral. Then it subsides and goes back to its normal resting point, then not too long later it spikes again. Thanks for all the info though, every bit does help.

PS- Surf I pm'd you.

 

[Diff Whack Daddy]

If you don't rev the engine does it drop back down as well. What I am asking, is does reving the engine make it drop down faster, or will it not drop at all while idling?

 

[Diff Whack Daddy]

One other thing, did you replace your radiator cap? The cap is designed to hold pressure, increasing the boiling temperature of the water and inhibitting the creation of steam. I think it's somewhere around 17 PSI. If it is old and not holding pressure, the temp spikes could be steam being created and any reoccuring air created by that is going to burp itself the next time it hits the radiator. It can be a vicous cycle. I would try replacing the radiator cap if you already haven't.

 

[jtb1689]

Cap was the first thing I did at the first signs along with the thermo. The one on the old radiator was 13 so I put another 13 on, which is what the guy at my local parts store pulled on his computer for a 93 explorer anyway to be sure. It does go back down if I don't rev it. Its just that if I see it start to climb, I can put the rpms up and it will start to come back down essentially on my command. If I leave it, which I also do just to see how high it spikes, it will spike, rest on the spike, then come back down. So: Revving brings it down on my command, but it will still come down when idling after it rests for a couple seconds in the high end of the spike.

 

[Diff Whack Daddy]

Okay, I would call that normal and it sounds like with it being a new thermostat it may be a little stiff. Over time, it should loosen up and start popping sooner.

 

[jtb1689]

In a little while here I am going to try something that a local mechanic tipped me off to. Drain the system, pull both heater hoses off the fire wall, hold them up so they are the highest part of the cooling system, then fill her back up till the coolant/water comes out the heater hoses. Hopefully it works, if not, keep the ideas coming.

 

[jtb1689]

Okay, I would call that normal and it sounds like with it being a new thermostat it may be a little stiff. Over time, it should loosen up and start popping sooner.

Even if it did the same thing with the old thermostat in there?

 

[Albino 94LTD]

Don't know if it makes a difference but did your guys' do it consistently? I spike it seems like every 2 or 3 minutes.

Yes

 

[Diff Whack Daddy]

If you really want to eliminate the thermostat, take it out and see if it spikes. However, I am betting it would never even get to normal operating temperature. The spikes your seeing and then rapid cool down is the thermostat opening.

Are you running anti-freeze, or just water? If it's just water, that also changes the chemical composition of the coolant and may cause the temp sensor to be a little more touchy.

 

[jtb1689]

Running both. Keep it as close to a half and half mixture as I can with my very accurate technique of pour some of this coolant, now some of this water, ok good . And I totally agree with the thermostat thought, it just befuddles me as to why the old thermostat would do the exact same as the new one which led me to the idea of air in the system. I guess I will just do what I can to rid the system of air, then ride out the spikes till the thermo breaks in. Thanks for all your help guys. I will keep the info on this quest updated.

 

[jtb1689]

Alright so it appears the big issue was too much air. Too cure this I drained the radiator and whatever else went down with it via the radiator drain plug. I then removed both heater hoses and held them as high as a could, hooked them up with a bent up hanger to the hood to hold them high. Then I had someone slowly dump coolant into the radiator while I would squeeze and let off and squeeze and let off repeatedly on the lower radiator hose. Once the person above let me know the radiator was full (actually when I squeezed the lower hose and coolant came dripping down onto me underneath) I went through a series of slowly squeezing, followed by rapid release of the upper radiator hose and lower radiator hose, squeezing just enough to see the coolant rise at the top of the radiator, but not overflow (it should be pretty close to begin with as it should be full). Next came the messy part. I unhooked one heater hose (the one that delivers coolant to the firewall, passenger side). I quickly moved it into place and secured it on the firewall. Now, as this happens though, coolant will spill everywhere since that hose is full and it will all just go out the other port so, when it starts to spill out the other port once its hooked up, you need to plug the port with your finger. Next came the other hose, did the quick "remove finger, smash on hose" technique for as little spill as possible. Now, time to add more coolant to radiator as level had gone down. Did the series of squeeze and release, this time including the heater hoses. I did this till the coolant continued to rest in the same spot after each release. VOILA! No super ridiculous temp spikes. It still spikes, just not as eradically and not as high as before, it always stays in the normal temp range. I figure the rest will burp out over time like you guys say and as Diff Whack Daddy pointed out my thermostat probably needs some breaking in. Thanks for all your help guys and if you made it to the bottom of this run on paragraph congratulations and thanks for your time

 

[mikeinri]

Glad it's better. I agree with most of the suggestions here. In addition, two things that no one mentioned that jumped right out at me:

Did you install the t-stat with the weep hole up? That helps the burping.

How old is your fan clutch? When temps spike at low idle/speed, that's a sign you're not getting enough air flow.

One other question. When you removed the old radiator, was the front of it clean? If not, check the rubber hoses running to the tranny cooler. If they are leaking, replace them (and the clamps). They will leak with age, and when the ATF gets on the front of the radiator, it attracts and holds onto road debris, eventually clogging the radiator and drastically reducing its cooling ability.

Hope this helps.

Mike

 

[jtb1689]

I did make sure to get that thermostat hole up. I didn't at first but when I looked at it, it hit me that it probably should be so that is for sure ok. Fan clutch is fine. The radiator did have debris on it but I think it may have been from the radiator leaking since I was always adding coolant/water. It should be fine now, if the temp doesn't balance out over the next little while I will check up on a few things. Till then, thanks for all your help guys in getting it all up and running. It's always greatly appreciated.

 

[d.bright]

I replaced the entire cooling system on my 92, and had the same issue, After changing out the thermostat once more, I decided to change out my temp sending unit (the one that sits on the top of the intake manifold), after doing this, my temp guage stopped spiking. I did have some air that escaped over time and I just made sure I topped off the radiator a few days later.

Also, a huge time saver when burping the system is to use one of those yellow funnel systems that attach to the top of the radiator, you can see the bubbles coming out and really do a good job of burping the system.