Overheating after steep climb

Discojunky

Well-known member
Apr 20, 2004
384
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62
Greenville SC
Hey I have a 98 D1 and I went wheeling this weekend. It was the second day and right before I left I went up a really steep incline. 30 min later I noticed the temp was getting hotter than normal. It was 40 deg outside so I figured once I hit the freeway it would cool down......it got worse fast.

As the needle cleared the top edge of the normal going towards hot but way before it got to hot line I shut it down and coasted to a stop. Checked the water and the fluid was green, not rusty and full. No leaks, no dripping. Top hose was hard (from pressure) and hot. After it cooled down I tried it again and went really slow but after a few minutes it started climbing fast again.

Could it have air in the system from the steep climb? Seems weird I drove it hard off road for two days and then right after the climb all this happened.

Coincidence?

I guess I'll try a thermostat, new hoses and cap (I hear they can clog) and just fill it with just water and see how it acts....before I waste money on anti-freeze testing it out. I'm trying to start cheap and change things that could afford to be changed anyway before I go farther.
 

Tugela

Well-known member
May 21, 2007
4,754
562
Seattle
It the temperature rise is repeatable, you blew the head gasket.

Peter, he doesn't even know if that is his problem!

No big deal, half a weekend of a job.

Plus the time it takes a machine shop to resurface the heads, which you understand is an essential part of head gasket replacement. Alternatively you could buy resurfaced heads before you start the job, which would eliminate the turnaround time but would increase the up-front costs.
 
Last edited:

the deputy

Well-known member
Sep 20, 2017
86
0
michigan
If you aren't seeing any leaks, white smoke from the exhaust on start up or while driving, or coolant in the engine...I'd definitely do the stat and cap first and go from there.

Hoses, only if you need them...they wouldn't cause an over heating issues (unless leaking or collasping, but you say you have non of that). Check for blockage of the radiator, externally (leaves, brush, etc...that may have been picked up while wheeling). Granted, if you're changing the stat...it would be a good time to flush the system.

As far as hill climbing causing the issue...I'd say coincidence.

Good luck, hope it's nothing serious.

Brian.
 

ezzzzzzz

Well-known member
Apr 22, 2010
604
7
SE Va
I overheated my first D1 too many times to count. The headgaskets weren't the issue. It was the radiator but the fan clutch was worn too. I replaced all of the usual suspects before dropping in a aftermarket radiator. That solved the problem. As far as I know, that truck was still on the road many years later.
 

Kdo58

Member
Sep 18, 2017
10
1
Puyallup wa.
I replaced my radiator last week, it would over heat on long steep hills. I finally burp it, doing it by the factory manual. It does not over heat at all now.
 

Discojunky

Well-known member
Apr 20, 2004
384
0
62
Greenville SC
I'm worried about it being a head gasket. My upper radiator hose feels like its under way too much pressure but I don't have another to compare to. Oil is not milky and coolant is not oily. The upper hose gets warm maybe even slightly hot but you can hold it at operating temperature for 5 seconds at least with out it being unbearable. The heat still runs hot as well. My plan now is to remove thermostat, flush system replace radiator cap, and bleed the system and see if it still runs hot unless any of y'all have better recommendations.
 

p m

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Apr 19, 2004
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I'm worried about it being a head gasket. My upper radiator hose feels like its under way too much pressure but I don't have another to compare to. Oil is not milky and coolant is not oily. The upper hose gets warm maybe even slightly hot but you can hold it at operating temperature for 5 seconds at least with out it being unbearable. The heat still runs hot as well. My plan now is to remove thermostat, flush system replace radiator cap, and bleed the system and see if it still runs hot unless any of y'all have better recommendations.
Start with the OBD-2 something that allows you to keep track of the temperature.
 

p m

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Peter, he doesn't even know if that is his problem!

Nick, he certainly doesn't know, neither do you or I. What caught my attention was this:

Discojunky said:
After it cooled down I tried it again and went really slow but after a few minutes it started climbing fast again.

So, Nick, I don't know what your ideas of an advice are.
Bear with me, since I am not a show owner or an auto mechanic by trade.

Let me try to analyze:
Can the quick overheating AFTER another overheating be caused by, say, failed thermostat, or fan clutch, or plugged radiator?
Yes it can. But not very likely.
Can it be caused by a failed water pump?
Yes it can. But, personally, I have never once in my life seen a water pump that just went tits up. Doesn't mean it never happens, but it is at least not very likely.

What else can you think of? With the top radiator hose becoming hard? For the reference - at 195F, I can usually squeeze the top radiator hose at least to half its thickness (physically I am pretty far from a gorilla, and if I cannot, I begin looking for HG leaks).

So, this is where I'd start.
See if running the heater full tilt can keep the temperature down under medium load (regular city driving). If it can, thermostat needs to be looked at - it is ridiculously simple to replace one, just make sure whatever you put in has a little hole at 12 o'clock.

Then, once you know thermostat is good, buy or borrow an IR gun and measure the temperature drop across the radiator (right side - left side). I don't know what it should be, but I do know that on trucks without a slightest hint of cooling issue it is about 12-15F drop. The other metric is to measure the temperature differences top to bottom - if the bottom of the radiator is noticeably cooler than the top, you need either to have it rodded or replaced.

I don't know of a good way to test the water pump - in my experience, if you squeeze the top radiator hose half-way with the engine at the normal operating temperature and pull on a throttle cable momentarily, you should feel slightly-increased pressure in the hose. Alternatively, if the heater trick works, it means the pump is likely okay.

Regardless of the above, you can take it to a shop with tools to detect the presence of exhaust gasses in coolant.

I overheated my first D1 too many times to count. The headgaskets weren't the issue. It was the radiator but the fan clutch was worn too. I replaced all of the usual suspects before dropping in a aftermarket radiator. That solved the problem. As far as I know, that truck was still on the road many years later.
I pity the poor soul that inherited this engine. He or she might be lucky, or not - and go through multiple head gasket jobs before realizing that the block is cracked.

By the way -
The Deputy said:
If you aren't seeing any leaks, white smoke from the exhaust on start up or while driving, or coolant in the engine...

Not one out of about 10 RV8 head gasket failures I've seen had white smoke from the exhaust or coolant in oil.
 

ezzzzzzz

Well-known member
Apr 22, 2010
604
7
SE Va
^ I wouldn't pity that poor soul. I traded the D1 5 years ago for a M101cdn and some cash. He was still driving it last time we spoke (about 15 months ago) and never had any issues other than maintenance. He loved that truck as it was a Polo Edition and the only one I've ever seen other than a photo. No major engine issues during it at least 8 years of firsthand knowledge.
 

Tugela

Well-known member
May 21, 2007
4,754
562
Seattle
Peter, at last I have a few minutes to return to this thread - however interesting it may be, discussing head gasket diagnoses with strangers on the interwebs must compete with other priorities. I follow your chain of logic and agree with it. I'm glad that you point out that there are alternative problems in play and you propose a systematic approach to eliminating them in the order of most to least likely. Undertaking a HG replacement involves a fair bit of preparation, a not insignificant cost, and a decent chunk of time to do correctly (or a lot of time, if you're me). Hence my repurposing of your response in reply to your prognosis given the range of other possibilities that are worth eliminating first.

My advice is not very different from your follow-up progression of inquiry. If there are other indicators of HG failure present (loss of coolant, e.g.) then I might insert earlier in the progression: buy a DIY chemical test to check for exhaust gases in the coolant. I don't know if those kits are as accurate as what a specialist shop might do, but if you have other evidence pointing to the HG then this could be enough to make a decision. If the DIY tests are unreliable then I'd seek out a professional evaluation as you suggest.

I would go further and offer that - assuming HG need replacement - a useful approach is to think more expansively about the reasons for HG failure. From my limited, amateur experience with the subject, the overheating that leads to a HG failure is often precipitated by another factor. Replacing head gaskets won't completely remedy your situation if you don't also replace your 20-year old, partially clogged factory radiator and weak fan clutch. This is one more reason it's helpful to evaluate other components before defaulting to a failed HG conclusion: you learn what else you need to include in your project planning to reduce the chances of repeating the job in a couple months.

Last summer I replaced my D1's radiator, water pump, thermostat, and fan clutch. When I took a 6-day drive of the Washington Backcountry Discovery Route I was glad to see my ScanGauge hold steady at 196-7 while ascending 3,000-foot climbs in low range with 100-degree ambient air temperatures. When it's in good shape the D1's cooling system does its job pretty well.
 

WaltNYC

Well-known member
Mar 3, 2010
707
135
NYC
Nice discussion here. First you need to determine if you are losing/burning/consuming coolant. If the level in the reservoir is falling and you need to add coolant, there is a good chance the HG is blown. If you are NOT losing coolant there is little reason to believe your HG is the issue.

A) If you are losing coolant get an exhaust gas tester. While that is not always 100% conclusive, it may tell you all you need to know and it is only $30. If that looks 'good' (no exhaust gas in coolant) I'd get it to a shop for a leak down test.


****************************************************

B) If you are NOT losing coolant I'd start with the fan clutch, t-stat, reservoir cap, and make sure the electric fans in front of the radiator are still working (they should blow towards the radiator whenever the A/C is on and/or when the coolant temp rises above 220 deg).

All combined that'll cost you <$100.

If those don't do the trick the next item on my list would be the radiator. Some replace them with inexpensive aluminum units with plastic tanks that can be found on E-bay for as little as $250. Other (like me) would have the original re-cored ($350-400).

Electric fans will run $50-80 a piece (there are two). These really help when wheeling in hot weather with the A/C on or in stop-n-go traffic.
 

p m

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my truck would overheat on steep climbs, especially at elevation.

GM fan clutch resolved the issue
Let me suggest that GM fan clutch temporarily masked the issue.
A D1 with no known head gasket issues, good radiator, water pump, thermostat, should not overheat with the factory fan clutch. Even loaded with five adults going nearly flat out up I-70 (the A/C condenser fans may come on, temporarily).
 

Discojunky

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Apr 20, 2004
384
0
62
Greenville SC
Thanks everyone. Thank God it's not my DD so I have time to look into it. For more info I did run the heater wide open and it didn't help the overheating........just damn near killed me.........lol I had all the windows down and it was still like a sauna in there and it was 40 Deg outside.

I really hate to put in a water pump to find out it's a head gasket and vice versa. Lot's of great advise to chew on here and thanks for all the help.

I did have a "use or lose" credit with a company so I have a new radiator in the attic which will be going on just in case. The truck has never ever overheated in the past or even been above the normal line so I'm hoping it's not a HG but I guess all things go eventually.......as a troubleshooter it still seems odd it came on right after the climb but not the days of slow wheeling.
 

Howski

Well-known member
Oct 19, 2009
1,483
209
Alabama
Hate to go OT but where were you wheeling at? Wasnt aware of anywhere around Greenville like that
 

mgreenspan

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Feb 28, 2005
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Briggs's Back Yard
Let me suggest that GM fan clutch temporarily masked the issue.
A D1 with no known head gasket issues, good radiator, water pump, thermostat, should not overheat with the factory fan clutch. Even loaded with five adults going nearly flat out up I-70 (the A/C condenser fans may come on, temporarily).

The overheating on the highway makes me think it's not a fan clutch issue. The water pump is either not functioning properly or there is an internal issue (like head gasket). I think the it happened after ______ is unrelated. Unless there is an obvious amount of mud blocking the radiator I don't see how anything wheeling related would cause it to happen unless you also broke all the motor and trans mounts and the entire drivetrain shifted forward and caused the water pump to be knocked around breaking something internal.

I'd personally replace the pump and see if that fixes it. There are only so many pieces of the cooling system. It's either one of them or it's a "dreaded" head gasket.

I may have overlooked it, but was it verified that nothing is coming out of the weep hole on the pump or that it doesn't make any grinding noises as it moves?
 

kcabpilot

Well-known member
Mar 26, 2006
334
1
California
I went through a similar problem last year. In my case it would only overheat when climbing a hill. I could idle or drive around on flat ground all day but as soon as I came to any sort of incline it would rapidly overheat. I replaced the fan clutch, the thermostat, the pressure cap and the radiator all to no avail. I did a pressure test and a block test for exhaust gas in the coolant but always got negative results. I really wanted my truck back on the road and I had already done the head gaskets at around 100,000 miles. The engine then had around 180,000 so it made no sense to do gaskets again as it really should get new cam, rockers, timing chain and such, probably best to just do a complete overhaul so I bought a used 4.6 and installed it. My plan was to tear down my original engine and find out what was going on and rebuild it as a 4.6 but so far I haven't gotten around to it and the replacement engine is running fine.

My best guess (for my case) is that it was a head gasket. I know that the block tests I ran always came out negative but it seems that my problem only occurred under heavy load when climbing a hill and it was not possible to create those conditions and do a block test at the same time. just idling in the driveway never seemed to be a problem thus no positive results from the block tests.

I would also add that my problem started after a particularly grueling 1800 mile expedition out to Utah for two weeks of off roading in Canyonlands during which I admittedly was WAY overloaded with gear and that despite the issue the truck did manage to get me home and I was never left stranded, although I did have to nurse it a bit.

Anyway, a head gasket job on these is not that bad. On my truck the only things I curse at are the SAI pipes and coil packs. They make what would normally be a piece of cake job kind of a pain in the ass. I really think those pipes could be replaced with some hoses and the coil packs could be relocated but maybe it's just not worth it.